VBScript ships with many functions that you can
use to complete your scripts. These functions are highly reliable and can
tremendously reduce your work. This means that, before creating your own
procedure or function, first make sure it has not been written already
because if an existing function already implements the behavior you want
to apply, you should such a function.

Because VBScript is an interpreted language (and not a
compiled language), all of the possible built-in functions are already
known to the browser. Therefore, you don't need to include a file or
library.

The best place to find out what functions already
exist is by consulting the MSDN
library or web site for its documentation.

Conversion Functions

We saw already that the users of your web pages will be
presented with objects called controls. These objects allow the user to type
values or select something from a list. Anything the user types in a text-based field is primarily
considered as a string. Before performing any type of operation that involves
such a value, you should make sure you can identify what kind of value it is.
For example, you shouldn't try to multiply a string by a date such as FirstName
* January 16. Although you will not be able to avoid every single type of
problem that could occur in a page, you can reduce errors by checking the value
that a control holds.

The first thing you should do with a value retrieved from a
control is to convert it to the appropriate type. There are various conversion functions adapted to the
different possible kinds of values. The general syntax of the conversion functions is:

ReturnType = Function(Expression)

The expression could be of any kind, depending on how the
expression would be supplied. For example, it could be a string or value the
user would have entered in form. It could also be the result of a calculation
performed on another procedure or function. The function would take such a
value, string, or expression and attempt to convert. If the conversion is
successful, the function would return a new value that is of the type specified
by the ReturnType in our syntax.